Drapery support systems that permit opening and closing of the draperies are well known. Such systems commonly consist of an aluminum, steel or plastic headrail that contains a series of roller or sliding carriers. These carriers have drapery fabric or material connected to them by some form of a drapery hook or other means. Depending on the form of pleating, these carriers are spaced at approximately three inches. Also depending on the pleating system the individual carriers may or may not be not directly connected to each other. In the most common form they are indirectly connected by means of the suspended drapery fabric. A lead carrier or master carrier is normally connected to the foremost end of the drapery fabric.
The master carrier is most commonly attached to a drive cord that is guided inside the metal or aluminum headrail, between the side walls of the headrail. At each end of the headrail, the drive cord is normally guided through a free-wheel pulley at the non-drive end and through a drive pulley at the drive end. In its most common manually operable form, the drive cord is guided down vertically at the drive end where it loops down. By pulling one end of the looped down cord the drapery will be closed, by pulling the other end the drapery will be opened. Some drapery systems do not have a drive cord, but are operated by pulling a wand that is connected to the drive carrier. Instead of being actuated by a cord, some systems are driven by a steel wire or a belt.
Drapery systems may consist of one panel which opens towards one end only (one-way opening), or they may consist of two panels which then close towards the center and open by pulling the panels each to one end (center opening). In the case of very long windows, more than two panels may be hung from the same headrail, for simultaneous opening with a single drive motor.
To avoid excessive wear and tear of drapery fabrics, it is generally not recommended to open and close drapery panels by pulling on the drapery fabrics or materials themselves. Especially on cord actuated systems, the required force to pull a drapery open or close by means of pulling the fabric instead of the cord may require considerable force and result in damage to the fabric or the system.
Motor powered drapery systems are known in either a direct drive version or an indirect drive version. In a direct drive version, the motor is directly connected to the headrail and the rotation power is transmitted to the drive cord or belt via a gear mechanism. An indirect drive version includes cord-drive motors that are normally mounted at some distance below the drapery headrail and have a vertical loop of the drive cord that extends below the headrail, guided through a pulley attached to the motor. Cord drive motors are usually hard to conceal, tend to require more maintenance for cord adjustments, and are usually less powerful than direct drive motors. Cord drive motors are more commonly used to retrofit manual cord driven drapery systems.
Direct drive drapery motors are normally outfitted with a pulley or sprocket that provides traction to rotate the drive cord, belt or wire. The master carrier of the drapery system is normally attached to the drive belt, cord or wire by means of a fixed connection.
Because direct drive motors are normally fully concealed behind the drapery fabric it is often not apparent to a user that a drapery system is motorized. An unsuspecting user may be tempted to start pulling on the fabric to open or close a drape which will require rotation of the motor. However, since such rotation is prevented by the direct drive connection, this could create damage to the mechanism or fabric if excessive force were applied by the user.
To prevent such damage from occurring by inadvertent manual operation by a user, it is necessary to have a method or mechanism to permit easy manual movement of the drapery fabric without damage to the electric drive system, such as by means of a disconnect between motor and drive cord, belt or wire when there is no current applied to the motor. There are currently two methods to achieve this: the electro magnetic shaft disconnect and the overlap master disconnect.
The electromagnetic shaft disconnect consists of a motor shaft that connects the drive shaft of the direct drive motor with a cord drive pulley. By applying power to the motor, magnets in the electromagnetic disconnect get actuated and pull the shaft end into a matching opening of the drive pulley, thus establishing a fixed connection between motor and drive wire. The disadvantage of this system is that it is most commonly operated by drive motors that are started and stopped by means of current sensing. They require considerable torque surges and as a consequence tend to be noisy.
Prior art disconnecting devices exist most commonly in two versions. The first version consists of a spring loaded nipple attached to the traveling master carrier which matches with a depression in a connector block mounted against the inside of a perforated drive belt. Because of space considerations, the microdimensions make the system extremely sensitive to wear and permit only very light drapery weight loads.
The other commonly known version consists of a master carrier featuring a single levered arm provided with one single multipurpose spring. By pulling the far end of the drapery downward, the levered arm frees the locking pin from the portion of the master carrier that is connected to the drive belt. This way the drapery fabric can be moved by hand.
The disadvantage of this system is that there is only one spring to handle both the drapery load function and the locking spring function. This requires that the spring action be strong enough to carry the drapery load, keep it in position and pull the arm back into position, but not so strong that it would prevent the locking pin from sliding back into its connector. The use of a single spring for this dual purpose severely limits the maximum allowable load on the arm. Currently this is commonly limited to a maximum of 0.5 kg vertical load.
The load limitation imposed by the single arm and single spring concept of the prior art places severe limitations on the motorized drapery system. In many instances motorized systems are used to eliminate the need for manual operation of large and heavy drapery systems. Weight limitations impose severe restrictions on the range of applications. Furthermore the maximum allowable weight due to the spring capacity can easily be exceeded, which would cause the load to lower the levered arm and free the connection between master carrier and drive belt. This would result in a malfunction of the motorized system when power is applied.